Modeling of the time-resolved vibronic spectra of polyatomic molecules: The formulation of the problem and analysis of kinetic equations

A semiempirical parametric method is proposed for modeling three-dimensiona l (time-resolved) vibronic spectra of polyatomic molecules. The method is b ased on the use of the fragment approach in the formation of molecular mode ls for excited electronic states and parametrization of these molecular fra gments by modeling conventional tone-dimensional) absorption and fluorescen ce spectra of polyatomic molecules. All matrix elements that are required f or calculations of the spectra can be found by the methods developed. The t ime dependences of the populations of a great number (>10(3)) of vibronic l evels can be most conveniently found by using the iterative numerical metho d of integration of kinetic equations. Convenient numerical algorithms and specialized software for PC are developed. Computer experiments showed the possibility of the real-time modeling three-dimensional spectra of polyatom ic molecules containing several tens of atoms. (C) 2001 MAIK "Nauka/Interpe riodica".